Needled felts for the papermakers' industry generally have a length ranging from about 40 feet to over 200 feet, although felts of shorter and longer lengths are produced in some instances. Typically, such felts have a transverse width from 200 to 400 inches. In producing needled felts, generally a number of separate layers of fibrous batt material are applied and needled to an endless backing or base fabric, generally of a woven material. The number of different layers typically is 2-8, depending upon the thickness of each of the layers. In the conventional manufacture of such endless felts, each of the layers is comprised of a carded fiber web or batt applied to the underlying endless fabric in a transverse, cross lapped manner, which is then fully needled to incorporate and unite the fibers to the base fabric. The carded fiber web or batt may be applied to the base fabric either directly from a cross lapping apparatus, or from rolls of tacked or pre-needled batt which have also been formed by cross lapping of a carded fiber web or batt. In a cross lapping apparatus, the carded fibers are supplied to a floor apron by means of a feeding device which reciprocates transversely over the floor apron so as to form a longitudinally-extending web having folded, cross-layed layers of fibers. The transverse width of the cross-layed fiber web corresponds to the transverse width of the endless backing or base fabric to which it is to be applied, with the carded fibers being oriented in a cross machine direction. As noted, the cross-layed fiber web can be applied to the base fabric either directly from the floor apron of the cross lapper apparatus, or can be tacked together by pre-needling and wound onto rolls which can thereafter be unwound to apply the cross-layed fiber web to the endless base fabric.
Such a conventional method of manufacture of paper machine felts requires that a transversely-extending splice be made after the layers of cross-layed batts are introduced and needled to the woven base fabric. Such a transverse slice can cause running problems in the press section of a paper machine, such as, for example, press bounce, since the splice is parallel to the press roll center line. Also, an unevenness in the surface of the finished felt can result. Still further, difficulties can arise in the tensile or machine direction strength of the resulting finished felt because of the transverse orientation of the fibers with respect to the direction of travel of the needled felt on the paper machine.
More recently, in order to overcome or minimize the aforementioned drawbacks, it has been suggested to apply to the needled felt one or more surface layers or plies of carded fiber batt which are oriented in the machine or longitudinal direction of the finished felt. In particular, it has been suggested to apply at least one layer of longitudinally-extending, overlapping spiral windings of a carded fiber web or batt with the pitch of the spiral windings extending transversely to the longitudinal direction of the finished felt. This is believed to provide a more appropriate orientation of the carded fibers in the longitudinal direction of the finished felt, which, in turn, is believed to provide for a smoother surface finish for the felt with improved machine direction tensile strength, thus minimizing or eliminating the possibility of longitudinal unevenness and/or press bounce
For instance, U.S. Pat. No. 3,508,307 discloses a technique in which a carded fiber web or batt is trained about a pair of spaced feed rollers so as to form a series of side-by-side loops, which after a needling operation, may be axially pulled from the feed rollers, and thus provide an endless tubing. The resulting endless fabric consists of a plurality of narrow width, overlapping loops of a carded fiber web or batt which extend longitudinally and are transversely pitched. In the technique disclosed in U.S. Pat. No. 3,508,307, the plurality of overlapping loops are needled together by means of a stationary, transversely-arranged needle punching machine whose length is only somewhat wider than the width of the fiber web being looped around the feed rollers and, thus, significantly less than the overall width of the finished fabric. With such a technique, relatively complex equipment is required for enabling the formed tubular structure to be pulled off axially. Additionally, problems have been encountered with formation of wrinkles or other distortions in the surface quality of the resulting endless felt which can affect the running properties of such felt.
Another prior art technique for producing felts having layers of longitudinally-extending spiral windings of a fiber web thereon is disclosed in Canadian Patent No. 980,556. In accordance with the apparatus and technique disclosed in this reference, a carded fiber web or batt of narrow width is applied to an endless backing fabric by means of a feeding device which is adapted to be reciprocated throughout the width of the backing fabric as the backing fabric is driven in a longitudinal direction, so as to produce a series of longitudinally-extending spiral windings on the backing fabric. The loops of fiber batt so applied to the backing fabric are then needled thereto by means of a full-width needling machine which has a working width corresponding to the width of the finished paper machine felt. In accordance with such known technique, however, full needling of the several loops of carded fiber batts to the base fabric cannot be accomplished until the several loops have all been applied to the backing fabric. This has resulted in the shifting, at least locally, of the applied fiber web relative to the backing fabric or previously applied plies or layers, such that wrinkles and/or localized thinning/thickening has occurred.
More recently, it has been suggested in U.S. Pat. No. 4,536,927 to apply overlapping machine direction loops of a fiber web to a base fabric on a conventional needling loom having a full-width needling machine by utilizing a transversely-reciprocating web feeder together with a reciprocating needling device of a working width corresponding to that of the applied fiber batt, so that the fiber batt is tacked and held in place as it is applied to the base fabric. In this regard, the small-width needling device and web feeder are reciprocated in unison throughout the working width of the paper machine felt so that the applied batt can be tacked to the backing fabric substantially as it is applied on the backing fabric, whereby the desired joints between the various loops of the fiber batt and the backing fabric can be achieved without the formation of wrinkles or of thicker or thinner portions in the resulting paper machine felt. After the desired layer or layers of machine direction fibers have been applied and tacked to the base fabric, conventional full-width needling is accomplished with the full-width needling machine to thus insure a uniform needling throughout the working width of the felt
Although the apparatus and technique disclosed in U.S. Pat. No. 4,536,927 overcomes some of the disadvantages of the earlier apparatus and techniques for providing machine direction fiber layers, it will be appreciated that with the technique and apparatus of U.S. Pat. No. 4,536,927, the full-width needling machine is idle while the longitudinally-extending spiral windings of fiber web are applied and tacked to the base fabric. This is for the reason that operation of the full-width needling device before all of the longitudinally-extending spiral windings have been applied to the base fabric would otherwise result in nonuniform needling of the spiral loops of machine direction batt, i.e., overneedling of the first applied loops and/or underneedling of the lastly applied spiral loops. Such overneedling and/or underneedling of different portions of the resulting endless felt can adversely affect the felting properties of the papermakers' felt and, thus, are undesired. On the other hand, requiring that the full-width needling machine remain idle while the spiral windings or loops of longitudinally-extending fiber batt are applied and tacked in place can adversely affect the efficiency of the plant or system for manufacturing of papermakers' felts.
More particularly in this latter regard, plants for manufacturing of papermakers' fabrics and felts traditionally include a number of different types of machines and equipment. For instance, such plants generally include a weaving loom for weaving of the base fabrics which, for example, may comprise woven monofilament mesh fabrics, a finishing machine onto which the base fabric produced on the weaving loom is placed for heat treating or setting of the woven base fabric in order to fix the size of the fabric, and a needle loom for needling fibrous material to be base fabric to fully integrate and unite the fibrous material into the base fabric. In addition, such plants also generally include a batt-making line for producing a carded fiber web or batt of narrow width, and a cross lapping apparatus for producing a cross-layered fibrous web of a width corresponding to the width of the base fabric. The cross-layed fibrous web may be applied directly from the cross lapping apparatus to the base fabric, or may first be tacked together, rolled onto a separate roll and then later unwound for being applied to the base fabric. The batt-making line may, in turn, include equipment for opening of textile fibers, equipment for blending of the fibers, and equipment for carding or orienting of the fibers to produce the carded fiber web or batt.
Needle looms are complicated, sophisticated pieces of equipment which generally have a plurality of separate needling stations, each of which is generally comprised of a plurality of juxtaposed needling units or devices mounted to a machine frame so as to extend across the working width of the machine. The needling units each include a multiplicity of needles arranged in rows and columns which are moved up and down to pierce the fiber layer applied to the endless base fabric in order to lock the fibers to the base fabric. Generally, several passes are made past the needling stations in order to fully and properly needle the fibrous layer to the base fabric. Further, when needling cross-layed fibrous webs to the base fabric, the full-width needling devices are initially operated so as to tack the cross-layed web in place (generally, by utilizing fewer needles and/or shorter strokes, but at a faster speed, i.e., a higher throughput) in order to initially hold the layed fibrous material in place. After the fibrous material has been tacked in place, the needling devices are then operated utilizing the full compliment of needles and/or at full penetration to fully lock and unite the fibrous material to the base fabric. This is accomplished, however, at a slower speed than that at which the fibers are initially tacked in place and, thus, the needle loom has a slower throughput. After complete and full needling, the endless fabric having the fiber layer needled thereon is taken off and may be placed on a finishing machine for heat-setting of the finished felts and/or for other surface treatments, such as singing, compaction, washing and/or vacuuming.
In terms of the operational process in the manufacture of endless papermakers' felts, the slowest piece of equipment and, also, the most expensive piece of equipment, is generally the needle loom. For instance, needle looms generally cost at least twice as much as finishing machines and, in some instances, almost three times as much as finishing machines. Also, in terms of the speed of operation, in present day plants, only one finishing machine is required for every two to three needle looms. That is, one finishing machine in a plant can supply finished, heat set base fabrics for two to three needle looms operating at conventional speeds and/or can finish or surface condition produced felts from two to three needling looms. Simply put, conventional needling looms are among the most expensive pieces of machinery in a papermakers' felt production plant and, also, among the slowest operating. Consequently, it is most important in order to efficiently and economically produce felts to maintain the needling looms operating at full capacity and performing their intended needling functions at all times.
However, employing a system and technique such as disclosed in U.S. Pat. No. 4,536,927, in which machine direction fiber batts are applied on and tacked to an endless base fabric while the endless web is on a conventional full-width needling loom, ties up the needling loom and removes it from being able to function in its intended manner. This is for the reason that the full-width needle loom is rendered idle during the time that the machine direction fiber batt is applied on and tacked to the endless base fabric. Here it should be noted that when the needle loom is tied up, the batt-making line also is tied up in those instances where the batt-making line is feeding cross-layed batts directly from the apron of the cross-lapping apparatus directly onto the base fabric on the needle loom. Consequently, while the system and technique disclosed in the '927 patent does result in the production of satisfactory paper machine felts, it is not accomplished in an efficient manner which takes into account the operating and production characteristics in a papermakers' felt production plants. Of course, the inefficiency resulting from the needle loom being rendered idle while fibrous material is being layed on the base fabric is more profound and significant in connection with applying machine direction fibrous batt to the endless base fabric since the needle loom cannot be used at all during the entire process of laying the fiber batt thereon. For instance, with conventional cross-layed fiber webs, the full-width needling device can be immediately operated as the batt is applied (albeit utilizing fewer needles or shorter strokes to tack the fiber batt in place) since the cross-layed batt, as it is applied or layed on the base fabric, has a width corresponding to the width of the base fabric. However, with machine direction fibrous batts applied or layed onto the base fabric on the needling loom, the full-width needling machine must remain idle during laying on of the loops of fibrous batt until all such loops have been applied to form a complete fiber layer extending across the full-width of the base fabric.